1. Field of the Invention
The present invention relates to a device and a method for filtering a fluid. More particularly the present invention relates to a device for filtering a fluid wherein a plurality of fibers extend longitudinally in the direction of the fluid flow during filtration of the fluid.
2. Description of the Related Art
U.S. Pat. No. 4,219,420 discloses an arrangement for filtering a contaminated fluid or medium. According to the disclosure of this patent a plurality of fiber bundles are located on a support and extend within a filter housing in direction between an inlet and an outlet of the housing. The fluid to be filtered is introduced through the inlet in a direction towards the outlet. The contaminated particles become arrested among the fibers as it passes through the plurality of fiber bundles. In order to improve the “depth effect” of the fiber bundles, the fibers may have different lengths. Here the quality of the filtered fluid depends on the density of the fiber bundles. However, in order to increase the quality of the filtration process, the density of the fibers must be increased, which requires more fiber bundles to be inserted into the filter housing.
An improvement to the filter of U.S. Pat. No. 4,219, 420 has been proposed in U.S. Pat. No. 4,851,136. Here a filter housing comprises a support with a plurality of fiber bundles attached to the support and extending within the filter housing in direction between an inlet and an outlet. A flexible water-proof membrane is provided within the filter housing to constitute a pressure chamber. When pressurized during the filtration process, the membrane presses the plurality of fiber bundles to form a frustrum-like filter chamber, and the fluid becomes filtered as it passes through the frustrum-like chamber. Here the density of the fibers and thus the quality of the filtration can be controlled by adjusting the pressure in the pressure chamber whereby the compressing of the fibers is adjusted.
Another filter having fibers extending longitudinally in the direction of the fluid flow, and wherein the density of the fibers is adjusted by compressing the fibers, is disclosed in U.S. Pat. No. 5,690,823. Here the fibers are arranged within an opening defined by a retaining member, and a displacement member comprising a conical-shaped part is arranged in the center of the fibers. By moving the displacement member in a direction along the fibers, the compressing of the fibers against the retaining member is adjusted whereby the density of the fibers and the quality of the filtration is controlled.
Thus, the principles of having a fluid filtration wherein a plurality of fibers extend longitudinally in the direction of the fluid flow, and wherein the quality of the filtration is controlled by adjusting the compression and thereby the density of the fibers are known.
The filtering device of U.S. Pat. No. 4,219,420 uses a pressure chamber in order to compress the fibers, whereas the filtering device of U.S. Pat. No. 5,690,823 has a conical shaped displacement member arranged in the center of the fibers in order to compress the fibers against a retaining member. Both of these filtering devices are relatively expensive to produce.
However, today there is much focus on the quality of water for use domestically as well for industrial purposes, partly due to the increasing pollution of the environment and partly due to increasing public awareness with regard to the quality of food and beverages. Furthermore, the population growth results in an even higher demand for a simple, inexpensive and effective device for filtering a fluid such as water.